Certain types of conventional ophthalmic surgery require breaking up lenticular tissue and solid intraocular objects, such as the intraocular lens, into pieces so that the tissue can be extracted from the eye. Extraction of lenses for cataract surgery is one of the most common outpatient surgical fields with more than 3 million cases performed annually in the United States alone. The lens resides within an anatomical structure referred to as the capsular bag, which separates the vitreous cavity from the anterior chamber (located between the capsular bag and the cornea). It is undesirable to allow fluid communication between the vitreous cavity and the anterior chamber, so during the process of extraction of the lens, care is taken to maintain the integrity of the posterior surface of the capsular bag. However, the capsular bag is composed of thin, delicate tissue. As a result, the physician must exercise extreme care in removing lens tissue to avoid unintended damage to the capsular bag. Further complicating the procedure, the lens is typically removed from the anterior surface of the capsular bag through a generally circular incision. The procedure, and the incision resulting from the procedure, is referred to as a capsulorhexis. Typically, the capsulorhexis does not exceed 2.8-3 mm in diameter. Generally, cataract surgery and other surgical procedures that treat the lens are performed by making a small incision in the edge of the cornea, providing access to the anterior chamber and to the anterior surface of the capsular bag. Afterward, capsulorhexis is performed, and then that opening is able to be utilized for surgical access to the lens.
During cataract surgery a commonly used method for lens extraction is phacoemulsification, which uses ultrasonic energy to break up the lens, after which the lens fragments are aspirated. Other methods of lens fragmentation and extraction have include the use of mechanical instruments, such as hooks or knives, or energy-delivery instruments, such as a laser, to break up the lens into fragments and then extract through an incision in the cornea in an ab-interno approach.
However, existing tools and techniques do not ensure full-thickness fragmentation of the lens. These techniques approach the lens from the anterior surface of the eye, and therefore the dissection forces exerted by mechanical instruments are limited such that they are often insufficient to accomplish a full-thickness segmentation. Further, due to the surgical approach through the incision at the edge of the cornea, a mechanical instrument is delivered at an angle substantially parallel to the plane defined by the capsulorhexis. As a result, a conventional surgical snare, loop or wire retrieval tool is not in an orientation in which that device could be looped around the lens to provide for fragmentation or extraction. Further, even if such a conventional tool could be looped around the lens, which it cannot, the wire of the snare would run the risk of applying excessive, damaging force to the capsular bag as it would be moved into position. Energy-delivery instruments are limited in their ability to cut sections of the lens which are physically close to other delicate anatomical structures such as the capsular bag. For instance, a laser is generally not used to cut the posterior edge of the lens because it is in close proximity to the posterior edge of the capsular bag, leaving a lens that is not fully fragmented and must be fragmented carefully using secondary techniques.
For these reasons, phacoemulsification has become the most popular method of lens removal. However, phacoemulsification has its own drawbacks. As fluid and substances are aspirated from the capsular bag and the anterior chamber, other fluids such as saline are inspirated to maintain a constant volume or pressure. The flow of the fluids in the eye during inspiration and aspiration may create turbulent flow which may have a deleterious effect on the tissue within the eye, such as the corneal endothelium. The ultrasonic energy used in phacoemulsification can have its own negative consequences on ocular tissue. Further, phacoemulsification requires expensive and bulky capital equipment, limiting the locations in which phacoemulsification can be performed.